Starter and ignition means for turbojet engines



C. N. LAWTER Oct. 14, 1952 STARTER AND IGNITION MEANS FOR TURBOJETENGINES Filed Feb. 4, 1948 I N V EN TOR. C QTZESJYZQZZ/Ex B PatentedOct. 14, 1952 STARTER AND IGNITION MEANS FOR TURBO-JET ENGINES- (lurtisi N jia wter, ,Trentom l f. ,J., ,a'ssignor. tn BaekardMo'tor CarCompany, Detr0it,'Mich.,'a corporation or Michigan ApplicationFcbruaryl, 1948; Serial No. 6 ,317

1 claim.

The invention relates to astarting'mecha'nism and ignition means for aturbo-jet engine, and the general object of the invention is'to providea'simplified ignition system for a turbo-jeten gine, utilizing a singlemore' or-le'ss standard automotive type of distributor for supplying.cur rent to all of the spark plugs; instead of the individual vibratorfor each plug heretofore em-' ployed.

It is also an object" to provide aflcombined starting mechanism andignition means under the control of a single switch.

Another object is'to provide a combined starter and ignition means for aturbo-jet engine, which may be arranged to be used with anypredetermined number of spark plugs and to energize each of such plugsany predetermined number of times per revolution of the starter shaftduring the period of operation of thest'a-rter;

A further object is to provide a combined starter and ignition meansfora turbo-jet engine,

having a starter motor and distributor- "which may be constructed as asingle unit-withadrive shaft common to both;

Still another objectisto provides; novel starter and ignition means for'a turbo-jet engine, whichmay be made up of more-or-lessstandard'automotive units modified to suit the requirements of aturbo-jet engine, thereby facilitating-"menu facture andreducin'g-thecost ofthe structurei Other objects and advantages will: become apparentfrom the following description taken in connection with the--accompanying'idrawing, in

which:

Figure 1 is a diagrammatic. front'elevational view of a turbo-jetenginehaving a starter'and ignition means embodyingthe' features of 1the invention.

Fig. 2 is a side elevational view, partially in section, of one formof'starter motor and distributor utilized in the starter and ignitionmeans shown in Fig. 1.

Fig. 3 is a wiringdiagramof theconnections utilized in the means shownin Fig; 1.

Fig. 4 is a wiring diagram showing'amodified arrangement of connectionsutilized in the distributor.

Fig. 5 is a view 'similar-to Fig. 2-but showing a modified form'of-structure; H

In a turbo-jet engine, where the turbine driven by the power streamgenerated within the engine is utilized to drive an; air compressor forsupplying air for combustion in the engine, an

electric starting motor operated by battery current may be employed forstarting -=the engine by rotating the shaft connecting-the" turbine andair compressor up to the speed where operation of the engine isself-sustaining. In an engine of this character, the starter motor isoperated to bring the turbine shaft up to a given speed before fuel isintroduced into the. combustion chamber section of the engine. Afterfuel is so introduced, the starter motorcontinues to exertv its drivingforce since the engine has .to be brought up to a still higher speedbefore it is self sustaining in operation. During the period betweenthese two speeds, partof the driving load is carried by the engineitself, but'until the engine reachesthe higher speed mentioned it isincapable of sustained operation. At such high er speed'the enginereaches the point where the starter'motor may then be disconnected fromthe turbine-compressor shaft and stopped.

After the operation of the engine becomes self sustaining, the heat inthe combustion chamber is sufficient to ignite fresh fuel supplied tothe burners therein Without the necessity of utilizing any otherignition means. However, during the period from the time when fuel isfirst introduced into the' combustion chamber until the sel'fsustainingspeed is" attained, an ignition means may be necessary. Such ignitionmeans usually is in the form of a spark plug which may be similar'incharacter to that utilized in automotive engines. It is thus apparentthat the ignition means should operate during such period and may beshut off or dispensed with at the time that the starter motor. isdisconnected from the turbine-compressor shaft. Consequently, the 0perationof the ignition means may be contemporaneous with the operationof the starter, and the starter and ignition means may, therefore, beunderthe control of a single control element.

With a turbo-jet engine which is provided with more than one combustionchamber, a spark plug may, of course, be provided in each such chamber.If, however, only one combustion chamber is provided, such as an annularcom-.

bustion chamber, at least one spark plug must be used, but a pluralityof spark plugs may be, and preferably are, used so that the fuel willbejignited at more than one point therein. It is also desirable toeffect operation of such spark plugs with as great frequency aspossible. in order to approach a condition of constant ignition sincethe supply of fuel to the combustion cham.

ber is constant.

.Since the'ignition system need be operated only contemporaneously withthe starter and. therefore, may be under the same control as theSUQIJDBTLELS stated above, a distributor for ener,-,

gizing the spark plugs in the combustion'chamber 3 section of the enginemay be driven by the starter motor. The distributor as well as anignition coil utilized in a system of this character may, therefore, beconstructed as a unit with the starter motor. The distributor may begenerally similar to the automotive type of distributor.

Referring to the drawings, in Fig. 1 a turbo-jet engine isdiagrammatically shown at III and is provided with a plurality of sparkplugs II, two spark plugs being shown in the present instance. Theengine may be provided with a gearbox I2 containing gearing connected tothe turbine aircompressor shaft of the engine. An electrical startingmotor I3 may be mounted on the gearbox I2 and be provided with a'clutchconnection I4 (see Fig. 2) adapted to disconnect the shaft of thestarter motor I3 from the gearing when the motor tends to overrun thegearing. Such mode of connection of a starter motor with an engine isusual in automotive practice. As indicated in Fig. 3, the starter motorI3 is provided with field coils I5 connected by lines IG- and I! toopposite poles of a battery 20. The motor I3 is under the control of aswitch which is herein shown at 2I in the line IS. The shaft of themotor in Figs. 2 and 3 is shown at 22. One pole of the battery may begrounded as at 23.

The ignition means, which includes the spark plugs II, in additioncomprises an ignition coil, indicated generally at 24, and adistributor, indicated generally at 25. The ignition coil 24 comprises aprimary winding 26 adapted to be connected to one pole of the batterywith the other side of the winding grounded, and a secondary winding 21,one side of which is grounded. The other side of the secondary winding21 is connected to the distributor, as will be hereinafter described.

As mentioned above, one of the features of the invention lies in placingthe ignition system under the same control as the starter motor I 3. Tothis end, the connection of the primary winding 26 of the ignition coilto the battery is by means of a line 30 connected to the line I6 for themotor I3 so that flow of current to the primary winding is thussubjected to the control of the switch H. which also controls operationof the motor I3. The distributor 25 comprises a plurality of contactpoints adapted to be connected to the spark plugs I I and a rotorconnected to one side of the secondary winding 2'! of the ignition coil24, the contact points being arranged in a circle and adapted to besequentially connected to the secondary winding of the ignition coil byrotation of the rotor. In the present instance, the distribui tor 25 isillustrated as being provided with two contact points 3I connected bylines 32 to the spark plugs II. The rotor of the distributor is shown at33 and is connected to the secondary winding 2! by a line 34. The sparkplugs, of course, are grounded to complete the circuit therethrough.Since the ignition coil 24-is operable only while the motor I3 isoperating because of the single control switch 2I, the distributor 25need only operate during this period. For this reason, the rotor 33 maybe operated by the motor I3 and, consequently, may be carried on themotor shaft 22. As is usual in the case of an ignition coil operating inconnection with a battery, the circuit through the primary win-ding 26of the ignition coil is interrupted just before the rotor 33 contactsone of the contact points 3I so a to produce a fluctuation of current inthe primary winding 26 which may be transformed by the secondary winding21. To this end, the distributor also includes a breaker switch 35adapted to be opened by means of a cam 36. The cam 36, similarly to therotor 33, may be carried on the motor shaft 22. A condenser 37 ispreferably connected in parallel with the switch 35, as is customary indevices of this character. The breaker cam 36 is adapted to open theswitch 35 just before the rotor 33 moves into engagement with each ofthe contact points 3 I. Consequently, with two such contact points asshown in Fig. 3, the breaker cam will be provided with two lobes to openthe switch 35.

With the foregoing structure, it will be obvious that when the switch 2Iis closed to operate the starter motor I3, current also will be suppliedfrom the battery 20 to the primary winding 23 of the ignition coil 24 bythe line 30. Rotation of the motor shaft 22 at such time operates thebreaker cam 36 and the rotor 33 of the distributor so that high-tensioncurrent is supplied alter-- nately to the two spark plugs II to producesparks: therein and ignite the fuel in the combustion. When the chambersection of the engine Ill. engine reaches such speed as to becomeselfsustaining and the starter is no longer needed, then the switch 2|may beopened to stop the starter motor, the clutch I4 thereofautomatically disconnecting from the gearing in the gearbox I2 at suchtime. Simultaneously with the stopping of the starter motor I3, thecurrent to the primary winding of the ignition coil 24 iscut off androtation of the rotor 33 of the distributor as well as rotation of thebreaker cam 36 is stopped. Consequently, when the starting motor I3 isstopped and disconnected from the engine, supply of high-tension currentto the spark plugs II ceases.

In a broad sense, of course, supply of hightension current to the sparkplugs II may be stopped merely by opening the single control switch forthe starter motor, whether or not the distributor is driven by. thestarter motor. Thus, if the starter motor were driven from some othersource of power, for instance by the engine itself, the rotor 33 wouldcontinue to rotate but no current would be supplied to the spark plugssince the switch 2| would cut oil the supply of current from the battery20 to the primary winding of the ignition coil 24; The same broad resultcould also be obtained by having separate switches controlling the flowof current from the battery to the starting motor and to the primarywinding of the ignition coil 24, if the distributor were mounted on thestarter, motor shaft, as shown in the drawings. In that instance, eventhough current continued to be supplied from the battery to the primarywinding 26 after the starter motor was stopped, neither the breaker cam26 nor the rotor 33 would operate in that case and, consequently, nohigh-tension current would be supplied to the spark plugs I I. It ispreferred, however, to utilize the arrangement shown diagrammatically inFig. 3, where a switch common to both the starting motor and theignition coil is employed and the distributor is driven by the startingmotor.

'As heretofore mentioned, if the turbo-jet engine has a plurality ofcombustion chambers, then at least one spark plug may be provided foreach such chamber to ignite the fuel therein, although in some instancesonly certain of the chambers are provided with spark plugs and the fuelin the other chambers is ignited through the use of transfer passagesconnecting the chambers. However, if the combustion chamber is annularin form and is coaxial with the engine so that the combustion chamber isrelatively large, it may be desirable to utilize more than one sparkplug for the single chamber, so, that ignition of fuel takes place atmore than one point in such chamber. The arrangement shown in Figs. 1and 3 of the drawings, since to contact points 3| are shown and only twospark plugs H are employed, is such that it may be used either with anengine having separate combustion chambers or a single chamber with twopoints of ignition therein. Since fuel is supplied constantly to theengine after it reaches a predetermined speed, it, of course, would bedesirable to have a constantly or continuously operating ignition means.While the present system would not permit of such constant operation,since the source of current is a battery which requires interruption toobtain higher voltage by inductive means, an approach to constantoperation may be attained by an arrangement illustrated diagrammaticallyin Fig. 4. In Fig. 4 I have shown a distributor 50 provided with aplurality of contact points 5|, in the present instance eight suchcontact points being shown. Such a distributor may be utilized with aplurality of spark plugs where the number of spark plugs is less thanthe number of contact points 5| but the latter number is a multiple ofthe number of spark plugs. With this arrangement, the contact points areconsecutively connected to the respective spark plugs so that at leasttwo non-adjacent contact points are connected to each of the sparkplugs. Thus, with the distributor shown in Fig. 4 utilized with twospark plugs as shown in Fig. 1, alternate contact points 5| areinterconnected by the lines 52 and are then connected to one of thespark plugs II by a single line 53. The remaining contact points 5| areinterconnected by the lines 54 and are connected to the other spark plugII by a line 55. With only two contact points, such as the contactpoints 3| shown in Fig. 3, a spark will be produced in each spark plugonly once for each revolution of the starting motor. With thearrangement shown in Fig. 4, a spark will be produced in each spark plugfour times for each revolution of the starter motor. Operation of thespark plugs thereby becomes more frequent and approaches the constantignition condition mentioned above.

By placing the ignition coil under the control of the same switch forthe starting motor and by operating the distributor from the shaft 22 ofthe starting motor, the distributor and starter motor may be combined ina single unitary structure, as disclosed in Fig. 2. Thus, in thisinstance, the motor I3 is provided with a frame including an end cap 60,on which the distributor cover 6| may be mounted. Further unification ofthe structure may be attained by making the ignition coil in the form ofa pancake, as indicated at 62, and enclosing it within a portion of thecover 6|. In Fig. 5, I have shown a slightly difierent form ofdistributor, here shown at 63, mounted on the cover 6|] of the motorframe. The ignition coil in this instance may be separate from thedistributor and may be mounted directly on the motor l3, as indicated at64. In both of the forms shown in Figs. 2 and 5, the distributor rotor33 as well as the breaker cam 36 are carried on the motor shaft 22.

I claim:

Th combination of a turbo-jet engine having a plurality of fuel burnersand a centrally disposed rotatably mounted drive shaft and a unitarystarter and ignition means for said engine including a plurality ofspark plugs cooperating with the burners to initiate a burning of thefuel in the engine, comprising a starter motor having a frame and adrive shaft, said shaft being adapted to be detachably connected to theturbine shaft of the engine, a distributor mounted on said framecoaxially with said drive shaft, a rotor in said distributor, said rotorbeing carried by said shaft, an ignition coil, a battery connected tosaid coil, a series of contact points in said distributor that areadapted for cooperation with said rotor, the number of said points insaid series being a multiple greater than one of the number of sparkplugs with at least two of said contact points being electricallyconnected to each of said spark plugs, the connections between each ofthe spark plugs and said series of contact points swept by the rotorbeing consecutively arranged so that adjacent points are connected todiiferent plugs, and said distributor being operably connected to saidbattery and coil whereby the plugs connected to said series of contactpoints may be consecutively caused to spark a plurality of times duringeach revolution of the rotor.

CURTIS N. LAWTER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

